SYMPOSIA PAPER Published: 01 January 1985

A Mechanism of Void Lattice Formation Based on Two-Dimensional Self-Interstitial Diffusion


Experimental work by Jacques and Robrock has suggested that the self-interstitial atoms (SIA) in molybdenum migrate two-dimensionally on {011} planes. The present author has recently explored the spatial effects that could result if this mode of diffusion were extended up to void formation temperatures for molybdenum and other body centered cubic (bcc) metals, and concluded that void lattice formation is a plausible outcome. This paper will summarize both the qualitative and rate theory arguments and the available evidence to support the two-dimensional diffusion of SIA at high temperatures in molybdenum and niobium. Although it was argued previously that the effect of planar void alignment on all six sets of {011} planes should lead to a bcc void lattice, it was not possible to demonstrate this via the rate theory approach. This weakness has now been rectified in a computer study that followed the growth and position of individual voids placed in a block of material and subjected to two-dimensional SIA migration on the {011} planes. Results from this work will be presented showing that under these conditions there is little doubt that the void positions can indeed evolve, as predicted, into a bcc void lattice. There is no difficulty in extending the present model to include bubble and vacancy loop lattices, while extrapolation to the face centered cubic (fcc) and hexagonal close packed (hcp) metals is also possible if the requirement of two-dimensional SIA diffusion on the close packed planes can be met.

Author Information

Evans, JH
Materials Development Division, AERE Harwell, Oxon, UK
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Developed by Committee: E10
Pages: 525–533
DOI: 10.1520/STP37384S
ISBN-EB: 978-0-8031-4935-9
ISBN-13: 978-0-8031-0450-1